Zimmer Y, Akselrod S, Tepper R
Medical Physics Department, Tel Aviv University, Israel.
Ultrasound Med Biol. 1996;22(4):431-9. doi: 10.1016/0301-5629(95)02064-0.
In this article, a model for the amplitude statistics of the backscattered ultrasonic signal is presented. We propose to view a tissue as being composed of a large number of small units, each having slightly different characteristics. This variability within the tissue is expressed by fluctuations in the parameters of the local probability distribution function (PDF). Based on analogous expressions derived for radio propagation and optical scintillations, the local PDF is modulated by a lognormal distribution of the local standard deviation. Integrating the local contributions yields the amplitude PDF for the entire tissue. We show that the local entropy is a normal variable, since for four different local PDFs it is linearly related to the logarithm of the local standard deviation. When the local entropy histogram exhibits distinct and multiple peaks, the local entropy distribution can be used for region segmentation. This fact is demonstrated for ultrasonic images of ovarian cysts.
本文提出了一种后向散射超声信号幅度统计模型。我们建议将组织视为由大量小单元组成，每个小单元具有略有不同的特性。组织内的这种可变性通过局部概率分布函数（PDF）参数的波动来表示。基于为无线电传播和光闪烁推导的类似表达式，局部PDF由局部标准差的对数正态分布调制。对局部贡献进行积分可得到整个组织的幅度PDF。我们表明局部熵是一个正态变量，因为对于四种不同的局部PDF，它与局部标准差的对数呈线性关系。当局部熵直方图呈现出明显的多个峰值时，局部熵分布可用于区域分割。这一事实在卵巢囊肿的超声图像中得到了证明。
